Flexible nanoparticle sensing films help detect chemicals in fruit and vegetables

(Nanowerk News) Researchers from from Russia, Spain and Singapore developed flexible sensing films based on silver nanoparticles. The new invention can identify the presence of pesticide residue on the surface of agricultural produce in mere minutes.
The research results were published in Nanoscale ("Silver melamine thin film as a flexible platform for SERS analysis").
In order to create these sensors, scientists from ITMO, the Ioffe Institute, National University of Singapore and University of Rovira i Virgili added melamine and a small amount of silver nitrate into a Petri dish with a small layer of agar gel.
Silver nitrate is well-known in the medical field as a bactericidal agent and in photographic engineering as a component of developing agents. Even though the substance contains silver, it is relatively cheap and accessible.
Silver nitrate’s reaction with the other components results in the formation of white crystal precipitation. When the Petri dish is exposed to light, the crystals decompose, forming silver nanoparticles, and the chemical reaction is complete. The resulting material is dried very carefully, as at this stage, it’s very easy to damage it. After the drying, you get lightweight and flexible films. The entire process takes about a day.
The film’s operating principle is simple. A piece of it is applied to a fruit and wetted with alcohol in order to gather pesticide molecules on the film’s surface; then, this piece is put into a spectrometer. The change in the optical response, the form and character of spectra in the graphs makes it possible to tell whether there is pesticide on the product surface or not.
“We compared the detection threshold of our sensors with that of classical instruments: chromatographic, polarographic, voltammetric, and other methods for detecting pesticides. Our method is cheaper, quicker and more mobile. What’s more, there already exist portable and affordable devices that can be used to check the response of our films. We plan to continue the experiments on identifying other types of pesticides at various concentrations,” adds Anastasia Nenashkina, head of the project and a PhD student at ITMO University.
Source: ITMO University
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